Hand held rotary tools are widely used by many people including professionals, craftspeople, homeowners, and artists. These rotary tools typically include an outer housing designed to be easily held within a human hand. The housing retains an electric motor which is operable to drive a rotatable chuck of the rotary tool. The widespread use of hand held rotary tools is a result, in part, of the wide variety of accessories that may be used with the tools. The accessories include cut-off wheels, polishing wheels, grinding wheels, sanding discs, routing bits and other cutting bits.
The accessories may be removably coupled with the rotary tool using a collet. By way of example, a prior art hand-held rotary power or cutting tool 20 is shown generally in FIGS. 1-3A. The rotary cutting tool 10 includes a motor housing 12 to which a detachable handle 14 is attached. An electric motor (not shown) is enclosed within the motor housing 12. The motor receives electrical power through an electrical cord 16 (only a portion of which is shown in FIG. 1). The electric motor is turned on and off by a power on/off switch 18 mounted on the motor housing 12.
An end of the motor shaft extends from one end of the motor housing 12. Attached to the end of the motor shaft is a collet bit attachment structure 20 for removably securing an accessory, such as those identified above, to the motor shaft. The collet bit attachment structure 20 includes a collet nut 22 and a collet 24 centered axially within a central aperture of the collet nut 22. The collet nut 22 is mounted on a threaded end of the motor shaft. To secure a bit to the motor shaft, a shank of the bit is inserted into a central aperture 26 of the collet 24. The collet nut 22 is then tightened, first by hand and then with a wrench 28, until the bit is held securely. To remove the bit from the motor shaft, the collet nut 22 is loosened, using the wrench 28, until the bit can be removed easily from the central aperture 26 of the collet 24.
The use of a wrench to tighten a collet bit attachment structure allows for accessories to be securely coupled with a tool. So as to ensure the proper wrench is available to a user, some devices provide a storage compartment within the rotary tool. For example, the wrench 28 for tightening the collet nut 24 may be stored in the compartment 30 formed inside the handle 14. The size of the compartment 30 is such that the wrench 28 is frictionally held therein to prevent it from sliding out during operation of the tool 10.
While the system of FIGS. 1-3A provides a convenient manner of storing a wrench that is used with a collet bit attachment structure, some users prefer a storage system that provides a more obvious indication that the wrench is firmly held within the storage compartment. Typically, a positive indication of proper insertion may be provided by a configuration that suddenly reduces the resistance to insertion of a component into a tool once the component is properly inserted into the tool. The sudden lessening of resistance provides positive feedback to the user that the component has been inserted into the tool.
Positive feedback may be provided in various ways. By way of example, FIG. 3A shows a housing 34 that includes a compartment 36. A coil spring 38 is positioned partially within the compartment 36. Accordingly, as the wrench 28 is inserted into the compartment 36, the wrench 28 compresses the coil spring 38. As a cavity 40 in the wrench 28 is positioned adjacent to the coil spring 38, the coil spring expands into the cavity 40. Positive feedback is thus provided to the user as the user feels the expansion of the coil spring 38 into the cavity 40.
While providing advantages, the use of a coil spring 38 tends to generate scratches on the wrench 28. Additionally, positioning the coil spring 28 within the housing 34 requires modification to both halves of the housing 34. Moreover, because the coil spring 38 is positioned within both halves of the housing 34, assembly of the device requires the coil spring 38 to be positioned within one half of the housing 34, with a portion of the coil spring 38 extending out of the half of the housing 34. Thus, the spring coil 38 may become misaligned during assembly of the housing 34.
While the provision of positive feedback is desired by some users, the manner in which a tool is configured in order to provide such feedback is also important to the users. For example, if the resistance is completely removed, the component is likely to move and rattle within the tool. Many users, however, interpret excessive movement and rattling of the components of a tool as an indicator of an inferior product, even if the movement and noise has no bearing upon the quality of the tool.
Moreover, other components in rotary tools require some amount of movement in order to provide the requisite operability. By way of example, the on/off switch is generally moved between a first position wherein power is applied to the internal motor and a second position wherein power is not applied to the internal power. Thus, some movement must be allowed. The allowance of movement is accomplished by designing the various components to be mismatched in size. While the mismatch in size allows for operation of the component, the resultant looseness may cause undesired noise as the tool is operated leading to the belief that the tool is an inferior device.
What is needed is a power hand tool which provides a positive indication that a tool such as a wrench is securely held therein. It would be beneficial to provide this benefit while minimizing the number of components needed to manufacture the tool.
What is further needed is a power hand tool which reduces noise and looseness of components. It would be beneficial to provide this benefit while minimizing the number of different components needed to manufacture the tool.